No, he won't ignore it but it might take awhile to figure out what to do about it.

North Korea is a scary place. Their only ally is China and even China is fed up with them.

If we really wanted the North Koreans to cease their activities we would inform the Chinese that we will no longer sustain the current trade imbalance with them. The North Koreans are very dependent on the Chinese for food and energy resources. The truth of the matter is that the Chinese find the North Koreans a useful (although crude) tool against the West and use them accordingly.